催化学报

催化学报 ›› 2019, Vol. 40 ›› Issue (6): 826-836.DOI: 10.1016/S1872-2067(18)63195-X

• 第十一届全国环境催化与环境材料学术会议专栏 • 上一篇    下一篇

BiOI上Bi单质和缺陷的协同作用:增强的光催化NO去除和转化途径

孙明禄a, 张文东b, 孙艳娟a, 张育新c, 董帆a,d   

  1. a 重庆工商大学环境与资源学院催化与环境新材料重庆市重点实验室, 重庆 400067;
    b 重庆师范大学科研处无机功能材料重庆市重点实验室, 重庆 401331;
    c 重庆大学材料科学与工程学院, 重庆 400044;
    d 电子科技大学基础与前沿研究院环境科学与技术研究中心, 四川成都 610500
  • 收稿日期:2018-08-26 修回日期:2018-10-17 出版日期:2019-06-18 发布日期:2019-04-26
  • 通讯作者: 董帆, 孙艳娟
  • 基金资助:

    国家自然科学基金（21501016，21777011，21822601）；国家重点研发计划（2016YFC02047）；重庆高校创新团队建设计划（CXTDG201602014）；重庆市自然科学基金（cstc2017jcyjBX0052）；国家“万人计划”青年拔尖人才项目.

Synergistic integration of metallic Bi and defects on BiOI:Enhanced photocatalytic NO removal and conversion pathway

Minglu Suna, Wendong Zhangb, Yanjuan Suna, Yuxin Zhangc, Fan Donga,d   

  1. a Chongqing Key Laboratory of Catalysis and New Environmental Materials, College of Environment and Resources, Chongqing Technology and Business University, Chongqing 400067, China;
    b Chongqing Key Laboratory of Inorganic Functional Materials, Department of Scientific Research Management, Chongqing Normal University, Chongqing 401331, China;
    c College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;
    d Research Center for Environmental Science & Technology, Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 611731, China
  • Received:2018-08-26 Revised:2018-10-17 Online:2019-06-18 Published:2019-04-26
  • Contact: 10.1016/S1872-2067(18)63195-X
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21501016, 21777011 and 21822601), the National Key R&D Program of China (2016YFC02047), the Innovative Research Team of Chongqing (CXTDG201602014), the Key Natural Science Foundation of Chongqing (cstc2017jcyjBX0052), and the National Ten Thousand Talent Program of China.

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摘要：

BiOI具有独特的层状结构及较窄的带隙，是具有可见光响应的光催化剂.然而，高光生载流子复合率抑制了其光催化活性.大量研究表明，氧缺陷不但是催化剂表面最具活性的位点，而且可以通过减小禁带宽度扩大光响应范围.与此同时，氧缺陷也可以作为光致电荷陷阱，抑制电子-空穴复合，并作为电荷转移到吸附物种的吸附位点.金属的表面等离子体共振（SPR）效应为半导体材料更高效的光吸收和利用提供了一条崭新的途径，从而可以获得更好的太阳光转换和光催化效率.然而，SPR效应和由氧缺陷引起的多个中间能级协同作用还未被探究.本文研究了利用金属铋的SPR效应和引入缺陷共同提高BiOI的光催化性能.通过部分还原BiOI制备出具有较高可见光催化去除氮氧化物活性的Bi@缺陷型BiOI，研究了还原剂用量对Bi@缺陷型BiOI光催化性能的影响.发现用2mmol还原剂NaBH4制备的光催化剂（Bi/BiOI-2）具有最高效的可见光催化活性.
XRD、XPS、SEM和TEM表征表明Bi单质沉积在BiOI表面，整个体系由纳米片自组装为海绵状立体结构.BET比表面积增大，结合SEM推测是由纳米片的分层堆叠造成的.UV-DRS表明带隙宽度仅有1.8eV的BiOI具有可见光响应.EPR和态密度（DOS）结合可以证明氧缺陷及其激发多个中间能级的存在.中间能级可以促进电子在可见光下从价带到导带的转移.PL表明体系中Bi金属的SPR效应所激发的电磁场可以促进光生载流子的分离.通过DFT理论计算催化剂的电子结构，差分、电子局域函数（ELF）及电势表明Bi单质和Bi-O层间强的共价作用形成一个通道，使得热电子从较高电势的Bi单质向相对低电势的BiOI传递，Bi单质PDOS的计算证明价带变宽归因于Bi元素轨道的贡献，Bi的SPR效应激发BiOI的电子到更高能级并聚集在价带顶，这有利于光生载流子的分离.ESR表明提升的电荷分离和迁移率促进了羟基和超氧自由基的产生.结合表征及理论计算结果，活性的增强可归因于金属Bi和氧空位的协同效应.氧缺陷激发的中间能级促进了电荷转移，Bi金属的SPR效应使可见光吸收效率提高并且促进了光生载流子分离，这些是增强光催化性能的关键因素.此外，采用原位红外光谱法（FT-IR）对Bi/BiOI-2的NO吸附和反应过程进行了动态监测.根据中间产物分析和DFT计算结果，提出了金属Bi和氧空位协同作用提高Bi/BiOI光催化性能的机理.本研究为高性能光催化剂的设计和理解空气净化光催化反应机理提供了新的思路.

关键词: 表面等离子体共振, 金属Bi, BiOI, 光催化, 氧缺陷, 反应机理

Abstract:

Surface plasmon resonance (SPR) of metals may provide a way to improve light absorption and utilization of semiconductors, achieving better solar light conversion and photocatalysis efficiency. This study uses the advantages of SPR in metallic Bi and artificial defects to cooperatively enhance the photocatalytic performance of BiOI. The catalysts were prepared by partial reduction of BiOI to form Bi@defective BiOI, which showed highly enhanced visible photocatalytic activity for NOx removal. The effects of reductant quantity on the photocatalytic performance of Bi@defective BiOI were investigated. The as-prepared photocatalyst (Bi/BiOI-2) using 2 mmol of reductant NaBH4 showed the most efficient visible light photocatalytic activity. This enhanced activity can be ascribed to the synergistic effects of metallic Bi and oxygen vacancies. The electrons from the valence band tend to accumulate at vacancy states; therefore, the increased charge density would cause the adsorbed oxygen to transform more easily into superoxide radicals and, further, into hydroxyl radicals. These radicals are the main active species that oxidize NO into final products. The SPR effect of elemental Bi enables the improvement of visible light absorption efficiency and the promotion of charge carrier separation, which are crucial factors in boosting photocatalysis. NO adsorption and reaction processes on Bi/BiOI-2 were dynamically monitored by in situ infrared spectroscopy (FT-IR). The Bi/BiOI photocatalysis mechanism co-mediated by elemental Bi and oxygen vacancies was proposed based on the analysis of intermediate products and DFT calculations. This present work could provide new insights into the design of high-performance photocatalysts and understanding of the photocatalysis reaction mechanism for air-purification applications.

Key words: Surface plasmon resonance, Bi metal, BiOI, Photocatalysis, Oxygen vacancy, Reaction mechanism